It has a single leathery, channelled leaf and up to ten relatively small blue, self-pollinating flowers with white, toothbrush-like tufts on the top of the anther.Thelymitra graminea is a tuberous, perennial herb with a single erect, leathery, channelled leaf 60–150 mm (2–6 in) long and 5–8 mm (0.2–0.3 in) wide with a purplish base.

[2][3][4][5] Thelymitra graminea was first formally described in 1840 by John Lindley from a specimen collected by James Drummond and the description was published in A Sketch of the Vegetation of the Swan River Colony.

[6] The specific epithet (graminea) is a Latin word meaning "grassy" or "of grass".

[7] The shy sun orchid is locally common in its range, growing in shrubland, woodland and forest or on granite outcrops.

[2][3][4][8] Thelymitra graminea is classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.